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From the evidence available, it appears to be tolerably satisfactorily demonstrated that in women who copulate at frequent intervals the tube must be regarded as a species of receptaculum seminis, in which spermatozoa are always present and waiting for the ovum, and that fertilization usually occurs in the tubes and only rarely in the uterus.

—J. Whitridge Williams (1903)


Nearly half of all pregnancies each year in the United States are unintended (Finer, 2016). These may follow contraceptive method failure or stem from lack of contraceptive use. In 2011 to 2013, 7 percent of sexually active fertile women in the United States not pursuing pregnancy did not use any birth control method (Daniels, 2015).

For those seeking contraception, effective contraceptive methods are available and variably selected (Table 38-1). With these methods, estimated failure rates of perfect and typical use during the first year differ widely. To reflect these failure rates, the World Health Organization (WHO) has grouped methods into efficacy tiers (see Table 38-1). Implants and intrauterine devices are found in the top tier. They effectively lower unintended pregnancy rates and are considered long-acting reversible contraception (LARC). The American College of Obstetricians and Gynecologists (2017c) recognizes these tiers, recommends counseling on all options, and encourages highly effective LARC for appropriate candidates.

TABLE 38-1Contraceptive Failure Rates During the First Year of Method Use in Women in the United States

No contraceptive method is completely without side effects, but contraception usually poses less risk than pregnancy. However, some disorders or medications can raise the risks from certain contraceptives. The World Health Organization (2015) has provided and updated evidence-based guidelines, termed Medical Eligibility Criteria, for the use of all highly effective reversible contraceptive methods by women with various health conditions. Individual countries have subsequently modified these guidelines. The United States Medical Eligibility Criteria (US MEC) was updated in 2016 by the Centers for Disease Control and ...

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